The present invention relates to the field of integrated circuits, and more specifically, to improving the interfacing of integrated circuit in a mixed-voltage environment.
The integrated circuit business and semiconductor industry are continually driven to reduce cost, reduce power, and improve performance. The integrated circuit products include microprocessors, memories, programmable logic, programmable controllers, application specific integrated circuits, and many other types of integrated circuits. Price reduction is strongly driven by migrating products to scaled processes, which reduce die sizes and increase yields. Power reduction has been achieved by circuit design techniques, power management schemes, and parasitic scaling, among other factors. Performance improvement has resulted from design techniques, process enhancements, and parasitic scaling, among other factors.
Process technology is improving. Resulting from the continual scaling and shrinking of device geometries, device sizes and dimensions require the operating voltages to be scaled. Operating voltages have been scaled down from 5 volts to 3.3 volts. This has resulted in the need for mixed-voltage-mode systems. That is, integrated circuits will need to interface with various operating voltages. And, further reductions are expected in the future. This industry provides products and printed circuit boards (PCBs) that utilize both 3.3-volt and 5-volt integrated circuits and devices. It is expected that there may be a considerable transition period for the standard power supply to switch from one voltage level to a lower voltage level.
Process scaling is the dominant method of reducing the die cost. The cost is achieved by receiving higher yields associated with smaller die sizes. Presently, power supply voltages are being reduced as the scaling progresses towards device dimensions that necessitate the reduction of voltage differences across these dimensions.
All manufacturers have not switched over to the lower power supply, simultaneously. Thus the scaling of the operating voltage has resulted in creating a multiple voltage mode industry. Integrated circuit companies must provide products capable of addressing the needs during this intermediate phase before the industry transitions to a single lower power supply voltage. It is expected that this industry will require some time to successfully transition over to the lower power supply.
As can be seen, an improved technique of fabricating, and operating integrated circuits is needed to meet these demands. These integrated circuits should interact with devices that are designed to operate at either the standard or the new lower power supply. The integrated circuit should also provide a cost reduction path to customers that continue to design 5-volt-only systems. Integrated circuits should provide the manufacturer with the flexibility to chose the market to support with a minimum cost and the shortest time to market.
The present invention is a technique of interfacing an integrated circuit in a mixed-voltage mode environment. In particular, the integrated circuit is fabricated using technology compatible with an internal supply voltage. Externally, the integrated circuit will interface with an external supply voltage, above the internal supply voltage. The input and output signals to and from the integrated circuit will be compatible with the external supply level.
An integrated circuit of the present invention will include conversion circuit for converting a voltage at a level of external supply voltage to a level of the internal supply voltage. In one embodiment, the conversion circuitry uses negative feedback, and is self-regulating. This internal supply voltage will be used to power the internal devices on the integrated circuit. The integrated circuit will contain conversion circuitry to convert output signals to be compatible with the external supply voltage. Also, the integrated circuit will also be able to accept input voltages compatible with the external supply voltage. The integrated circuit will appear to a user and other integrated circuits as though it were manufactured using technology compatible with the external supply voltage. The present invention is a useful technique for providing backward compatibility of a process technology.
The present invention may be used in an integrated circuit having separated noisy and quiet supplies. For example, the I/O drivers may be coupled to a noisy supply while the conversion circuit is coupled to the quiet supply. This will help noise from the I/O drivers from coupling into the core of the integrated circuit.
A layout of the conversion circuitry is compact and also spreads current flow and heat distribution evenly around the integrated circuit. This helps prevent the formation of localized xe2x80x9chot spotxe2x80x9d areas.
More specifically, an integrated circuit of the present invention includes an output driver coupled to a first voltage supply; a level shifter circuit coupled to a second voltage supply; and a voltage down converter circuit, coupled to the second voltage supply. The voltage down converter generates a first voltage supply having a voltage level below the second voltage supply. Circuitry in a core of the integrated circuit is coupled to the first voltage supply.
Other objects, features, and advantages of the present invention will become apparent upon consideration of the following detailed description and the accompanying drawings, in which like reference designations represent like features throughout the figures.